Measuring instrument



0.1-. MIDDLETON.

MEASURING INSTRUMENT.

APPLICATION FILED APR. 15. 1918.

1,403,972, Patented Jan. 17,1922

Inventor: CAI/mus J." Mwrz ETC/Y UNITED STATES PATENT OFFICE.

CHARLES U. MIDDLETON, F FOXBORO, MASSACHUSETTS, ASSIGNOR TO THE FOX-3030 COMPANY, OF FOXIBORO, MASSACH USETTS, A CORPORATION OF MASSA-CHUSETTS.

manasunme INSTRUMENT.

To all whom it may concern 7 Be it known that I, CHARLES J. MIDDLE- roN,a citizen of the United States, and resident of Foxboro, in the countyof Norfolk and Commonwealth oflMassachusetts,

have-invented an Im rovement in Measuring Instruments, of w ich thefollowing description, in connection with the accompanying drawings, isa specification, like characters on the drawings representing likeparts.

This invention relates to measuring instruments and in particular tothat type of instrument wherein a hand moving over a face or dial givesan indication of the response of the measuring instrumentalities. As anexample of my invention I have here (illustrated it as applied. to apressure gage desi ned for use as an airplane speedometer.

reference to the following description of the illustrative embodimentthereof shown in the accompanying drawings wherein z- Figure 1 is afront elevation of the in strument; and V Fig. 2 is a'section disclosingthe interior mechanism in elevation. 1

Referring to the drawings, the instrument disclosed embodies a suitablecasing 3 closed in front by the bezel 5 through the lazing of which isdisplayed a face or dial The hand or pointer 9 rotated by shaft 11 isadapted to sweep over the scale on this dial and indicate the pressuremeasured by the instrumentalities illustrated in Fig. 2.

Referring to Fig. 2, the shaft 11 is here shown as carrying a pinion 13which is revolved by a sector gear 15 adapted to be rocked by connectingrods 17 and 17 attached to pressure sensitive members 19 and 19. As themembers 19 and 19 are similar,

a description of one will suffice.

of any suitable sort adapted to be distorted when exposed to theconditions which the instrument is adapted to measure, the amount ofthis distortion as transmitted by a motion-transmitting connection, suchas the connecting rod 17 and sector gear 15, serving as a measurement.Herein, however, 'I have shown a device subject to deformation underpressure and inthe form'of an expansion tube consisting of a number ofintercommunicatin'g diaphragms 21 and hav-- ing, as a whole, a fixedhead 23, by which M? invention will best be understood by The, deviceswhich move the hand may be.

it is supported in the instrument, and a movable head 25, to which rod17 is secured. A

"spring 26 is secured along one side this expansion tube and therefore,if the pressure w1th1n the same is varied, the movement is not so freeon this side as the other and the ,tube will bend laterally. The motiondue to this bending will be transmitted through the rod 17 to the shaft11.

Herein the two tubes 19 and 19 are disposed symmetrically about the axisof sector 15 and the rods 17 and 17 are connected to equal cranksextending oppositelyfrom that axis so that the motions of the two tubesreinforce each other. The purpose of this is to balance the effect ofgravitation Specification of Letters Patent. Patented Jan, 17, 1922,Application filed April 15, 1918. Serial No. 228,766.

on the pointer or hand 9 if-the instrument is tipped as it will be ifused on an airplane for example. Thus, if the sheet of drawings isturned and viewed from the right hand side, it will be seen that if theinstrument be in that position, the effect of gravity on the tube 19 isto rotate the sector gear 15 clockwise, but that this effect is balancedand equalized by the gravitational effect of the tube 19 which isapplied through connecting rod 17 upon the opposite side of the axis ofthe sector gear and through an equal lever arm. This construction isdisclosed in U. S. patent to Edgar H. Bristol, #1,240,7 90 to which Irefer for a fuller description.

The fixed heads 23 of the two tubes are carried on a standard 27providing ductswill be noted that on the dial there shown the spacesbetween the major divisions are substantially equal throughout theextent of the same. It may be supposed, for example, that the, dial isgraduated in miles per hour, it being understood that this refers tothe! speed of the airplane on which the instrument is mounted relativeto the air through which it moves. The longer divisions might then eachindicate ten miles. In instruments of this character, hitherto, theangular displacement of the hand due to an incremental variation inpressure has been much less at the lower ranges of the instrument. Inother words, an-arc which would measure ,ten' miles on the dial in aboutthe location of thenumeral II on a clock dial would be much shorter thanthe are which would measure ten miles at a location corresponding to thenumeral X on a clock dial.

' noticeable when the range of the instru' 'ment was large, was that thefirst 'partfof the scale was crowded and comparatively difficult toread. My invention provides. means whereby this part of the scale may beopened out,'as it were,-and the discrepancy between the variousincrements there- I I pansionitube and the other free arm extending inthe path of one of the intermediate, diaphragms of the tube 'which maybe pro: vided with a lug 37 adapted to make contact with the arm of thespring as thetubei,

' is deformed under pressure. Thus, after the initial movement ofthe/tube a yielding resistance to its further deformation will beintroduced (at, least in sol faras the diaphragms at the left of the lug37 are concern'ed), so that a greater. pressure than would otherwise berequired is inecessary'to' produce the same amount of distortion. Itwill therefore" be readily understood that, since the'incrementalspaceson the:dial representvariations in pressure, the distancetraversed by the hand for a given variation of pressure in the laterstages ofjmovement of the tube is correspondingly shorter than it wouldhave been had the a'butment35 been omitted.

' Preferably I also provide means whereby a still greater' resistance isintroduced after the Tresilient abutment" has yielded a prede te'rm-inedamount and this is, herein exemplifiedj'as means whichcuts out a part ofthe spring and provides a positive resistance where before there was ayielding resistance; I have herein shown a screw 39 carried by one ofthe arms of the spring, in which it may be-adjusted by rotation, and;extending toward the oppositearm. vAfter the springv has somewhatyielded, the end of the screw will seat against this opposite arm whichhas the'efi'ect of putting out of action the upper portion thereof. Inother words, a much shorter and therefore stiffer spring will thenoppose deformation ofthe expansion tube.

The result, particularly "certain point,

i In the type of instrument such as I have here illustrated, twoexpansion tubes are .used and as shown the member'19? is proto movementof the hand 9 increasing in a 5 number of steps, herein four. Forexample, it may be supposed that the parts are so .ad- .justed thatfirst, the extension. 37 will seat on the free arm of spring 35; next,the corresponding extension on tube 19 will seat on 0 the arm of spring35; thirdly, that screw 39 will come into play; and lastly, that 39 willact. It may be noted that the-provision ofthe retardingmechanismdescribed does-not af- 35 fect the balanced condition, asregards gravity, of the type of instrument shown. Viewmg the drawingfrom the right hand side again, and supposing the extension 37 to haveseated, it will be seen that the tendency 0 of thetube 19 alone istofall so that the extension would leave the arm of spring 35., r

. but this is balanced by the Weightof tube 19 which, transmitting throuh' the connecting, rods, keeps the extension 3 seated. Having thusdescribed a specific form of my invention, embodying mechanical detailswhich might be varied without departing from the :spirit thereof, the'principles exem- I plified thereby and which I desire to secure 00 byLetters Patent I shall, define in the fol.-

lowing claims I 1. In a' dialinstrumentwherein a hand is moved bythefldeform'ation of a" sensitive member, means to modify the responsive5 movement'of the hand comprising a bowed springhavi'ng a freearmpresented. in thev path of the-member and a member'carried by 'one armof the spring and arranged, to seat on x the other arm when the springyields to a 110,"

2. In a -dial instrument wherein a' handis moved by the deformation of asensitive member, means to modify the responsive movement of the handcomprising a bowed spring having a free arm presented in the path of themember, and a screw threaded in one arm and havingfan end presentedtoward the other armto seat on the same when the spring yields to acertain point. 1*20 3. dial instrument having a hand, an ex? pansiontube comprising a plurality of 'communicating diaphragmsand having afixed head and a movable head, a 'motion-transmitting connection betweensaid movable head and the hand, a bowed spring having an arm fixedlysupported adjacent said fixed head and a free arm cooperating withanintermediate diaphragm which seats on the same J as the expansion tubeis distorted.

' ansion tube com risin a luraiit of comrename 4. A dial instrumenthaving a hand, an expansion tube comprising a plurality of communicatingdiaphragms, means on one side of the tube to restrain relative movementof the diaphragms wherebythe tube as a Whole will be distorted laterallyby pressure, a motion-transmitting connection between said tube and thehand and abutment means for cooperation with an intermediate diaphragmand against which it seats in its movement.

5. A dial instrument having ahand annexmunicating diaphragms,a,motion-transmitting connectlon between said tube and the hand, ayielding abutment for cooperatlon With an intermediate diaphragm andagainst which it seats in its movement and means effective on yieldingof the abutment to increase the resistance of the same.

6. A dial instrument having a hand, an expansion tube comprising aplurality of superposed communicating diaphragms and means at one sideof the tube to restrain relative movement oi the diaphragms whereby thetube as a Whole Will be distorted laterally by pressure, amotion-transmitting connection between the tube and the hand and meanseffective after initial distortion of the tube to introduce addedresistance to relative movement of diaphragms of the tube.

' 7. A dial instrument having a hand, a pair of expansion tubes formoving the same and yielding means for resisting distortion of the tubesat intermediate phases of their movements arranged to function atdifferent times for the different tubes...

8. A dial instrument having a hand, a pair of expansion tubes for movingthe same,

yielding means for resisting distortion of the 1

